/*

 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.security.ssl;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import java.nio.ByteBuffer;

import javax.crypto.Mac;

import javax.crypto.SecretKey;

import sun.security.ssl.CipherSuite.MacAlg;

import static sun.security.ssl.CipherSuite.*;

/**

 * This class computes the "Message Authentication Code" (MAC) for each

 * SSL stream and block cipher message.  This is essentially a shared-secret

 * signature, used to provide integrity protection for SSL messages.  The

 * MAC is actually one of several keyed hashes, as associated with the cipher

 * suite and protocol version. (SSL v3.0 uses one construct, TLS uses another.)

 *

 * @author David Brownell

 * @author Andreas Sterbenz

 */

final class MAC extends Authenticator {

    final static MAC NULL = new MAC();

    // Value of the null MAC is fixed

    private static final byte nullMAC[] = new byte[0];

    // internal identifier for the MAC algorithm

    private final MacAlg        macAlg;

    // JCE Mac object

    private final Mac mac;

    private MAC() {

        macAlg = M_NULL;

        mac = null;

    }

    /**

     * Set up, configured for the given SSL/TLS MAC type and version.

     */

    MAC(MacAlg macAlg, ProtocolVersion protocolVersion, SecretKey key)

            throws NoSuchAlgorithmException, InvalidKeyException {

        super(protocolVersion);

        this.macAlg = macAlg;

        String algorithm;

        boolean tls = (protocolVersion.v >= ProtocolVersion.TLS10.v);

        if (macAlg == M_MD5) {

            algorithm = tls ? "HmacMD5" : "SslMacMD5";

        } else if (macAlg == M_SHA) {

            algorithm = tls ? "HmacSHA1" : "SslMacSHA1";

        } else if (macAlg == M_SHA256) {

            algorithm = "HmacSHA256";    // TLS 1.2+

        } else if (macAlg == M_SHA384) {

            algorithm = "HmacSHA384";    // TLS 1.2+

        } else {

            throw new RuntimeException("Unknown Mac " + macAlg);

        }

        mac = JsseJce.getMac(algorithm);

        mac.init(key);

    }

    /**

     * Returns the length of the MAC.

     */

    int MAClen() {

        return macAlg.size;

    }

    /**

     * Returns the hash function block length of the MAC alorithm.

     */

    int hashBlockLen() {

        return macAlg.hashBlockSize;

    }

    /**

     * Returns the hash function minimal padding length of the MAC alorithm.

     */

    int minimalPaddingLen() {

        return macAlg.minimalPaddingSize;

    }

    /**

     * Computes and returns the MAC for the data in this byte array.

     *

     * @param type record type

     * @param buf compressed record on which the MAC is computed

     * @param offset start of compressed record data

     * @param len the size of the compressed record

     */

    final byte[] compute(byte type, byte buf[],

            int offset, int len, boolean isSimulated) {

        if (macAlg.size == 0) {

            return nullMAC;

        }

        if (!isSimulated) {

            byte[] additional = acquireAuthenticationBytes(type, len);

            mac.update(additional);

        }

        mac.update(buf, offset, len);

        return mac.doFinal();

    }

    /**

     * Compute and returns the MAC for the remaining data

     * in this ByteBuffer.

     *

     * On return, the bb position == limit, and limit will

     * have not changed.

     *

     * @param type record type

     * @param bb a ByteBuffer in which the position and limit

     *          demarcate the data to be MAC'd.

     */

    final byte[] compute(byte type, ByteBuffer bb, boolean isSimulated) {

        if (macAlg.size == 0) {

            return nullMAC;

        }

        if (!isSimulated) {

            byte[] additional =

                    acquireAuthenticationBytes(type, bb.remaining());

            mac.update(additional);

        }

        mac.update(bb);

        return mac.doFinal();

    }

}